IEEE802_11n.c

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/************************************************************************************
* Copyright (C) 2021                                                                *
* TETCOS, Bangalore. India                                                          *
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*                                                                                   *
* This source code is licensed per the NetSim license agreement.                    *
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* No portion of this source code may be used as the basis for a derivative work,    *
* or used, for any purpose other than its intended use per the NetSim license       *
* agreement.                                                                        *
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* This source code and the algorithms contained within it are confidential trade    *
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*                                                                                   *
* Author:    Shashi Kant Suman                                                      *
*                                                                                   *
* ----------------------------------------------------------------------------------*/
#include "main.h"
#include "IEEE802_11.h"
#include "IEEE802_11_Phy.h"
 
/**
This function is called to initialize the MIMO and OFDM parameters relevant to 
IEEE802.11n. 
This function is called from the "fn_NetSim_WLAN_PHY_Configuration()" for HT PHY.
Initialize time parameters as per the Table 20-5—Timing-related constants 802.11n-2009 pdf 
also initialize 802.11n PHY header relevant parameters.
*/
void fn_NetSim_IEEE802_11n_OFDM_MIMO_init(NETSIM_ID nDeviceId,NETSIM_ID nInterfaceId)
{
    UINT nNSTS_MAX = 4;
    UINT nNSS_MAX = 4;
    PIEEE802_11_PHY_VAR phy = IEEE802_11_PHY(nDeviceId,nInterfaceId);
 
    // Initialize OFDM timing parameters According Table 20-5—Timing-related constants 802.11n-2009 pdf
 
    if(phy->dChannelBandwidth == 20)
    {
        phy->PHY_TYPE.ofdmPhy_11n.nCH_BANDWIDTH = HT_CBW20;
        phy->PHY_TYPE.ofdmPhy_11n.nNSD = 52; // NSD Number of complex data numbers  
        phy->PHY_TYPE.ofdmPhy_11n.nNSP = 4;  // NSP Number of pilot values
        phy->PHY_TYPE.ofdmPhy_11n.nNST = 56; // 52 + 4
        phy->PHY_TYPE.ofdmPhy_11n.nNSR = 28; // NSR Highest data subcarrier index
        phy->PHY_TYPE.ofdmPhy_11n.nFFT = 64; // FFT length  
    }
    else
    {
        phy->PHY_TYPE.ofdmPhy_11n.nCH_BANDWIDTH = HT_CBW40;
        phy->PHY_TYPE.ofdmPhy_11n.nNSD = 108; // NSD Number of complex data numbers 
        phy->PHY_TYPE.ofdmPhy_11n.nNSP = 6;   // NSP Number of pilot values
        phy->PHY_TYPE.ofdmPhy_11n.nNST = 114; // 108 + 6
        phy->PHY_TYPE.ofdmPhy_11n.nNSR = 58;  // NSR Highest data subcarrier index
        phy->PHY_TYPE.ofdmPhy_11n.nFFT = 128; // FFT length
    }
 
    // Assign all the timing relevant parameters
    phy->PHY_TYPE.ofdmPhy_11n.dDeltaF = phy->dChannelBandwidth/ (phy->PHY_TYPE.ofdmPhy_11n.nFFT * 1.0);//SubcarrierFrequencySpacing 312.5KHz (20 MHz/64) or (40 MHz/128)
    phy->PHY_TYPE.ofdmPhy_11n.dTDFT = 3.2;  // IDFT/DFT period 3.2 MicroSecs
    phy->PHY_TYPE.ofdmPhy_11n.dTGI = phy->PHY_TYPE.ofdmPhy_11n.dTDFT/4; // 3.2/4 = 0.8 MicroSecs  Guard interval duration 0.8 = TDFT/4  
    phy->PHY_TYPE.ofdmPhy_11n.dTGI2 = phy->PHY_TYPE.ofdmPhy_11n.dTGI * 2; // 0.8 * 2 = 1.6 MicroSecs Double guard interval 1.6 
    phy->PHY_TYPE.ofdmPhy_11n.dTGIS = phy->PHY_TYPE.ofdmPhy_11n.dTDFT/8; // Short guard interval duration   dDFT/8 = 0.4 
    phy->PHY_TYPE.ofdmPhy_11n.nTL_STF = 8;     // Non-HT short training sequence duration 8 = 10*TDFT/4 
    phy->PHY_TYPE.ofdmPhy_11n.nTHT_GF_STF = 8; // HT-greenfield short training field duration 8 =10* TDFT/4 
    phy->PHY_TYPE.ofdmPhy_11n.nTL_LTF = 8;     // Non-HT long training field duration 8 =2 * TDFT + TGI2 
    phy->PHY_TYPE.ofdmPhy_11n.dTSYM  = 4.0;   //TSYM: Symbol interval 4 =  TDFT + TGI       
    phy->PHY_TYPE.ofdmPhy_11n.dTSYMS = 3.6;  // TSYMS: Short GI symbol interval = TDFT+TGIS 3.6 
    phy->PHY_TYPE.ofdmPhy_11n.nTL_SIG = 4;   // Non-HT SIGNAL field duration 4  
    phy->PHY_TYPE.ofdmPhy_11n.nTHT_SIG = 8;  // HT SIGNAL field duration 8 = 2TSYM 8 
    phy->PHY_TYPE.ofdmPhy_11n.nTHT_STF = 4;  // HT short training field duration  4 
    phy->PHY_TYPE.ofdmPhy_11n.nTHT_LTF1 = 8; // First HT long training field duration 4 in HT-mixed format, 8 in HTgreenfield format
    phy->PHY_TYPE.ofdmPhy_11n.nTHT_LTFs = 4; // Second, and subsequent, HT long training fields
 
    if(phy->nGuardInterval == 400)
        phy->PHY_TYPE.ofdmPhy_11n.nGI_TYPE = SHORT_GI;
    else
        phy->PHY_TYPE.ofdmPhy_11n.nGI_TYPE = LONG_GI;
 
    // Set the STBC coding
    phy->PHY_TYPE.ofdmPhy_11n.nSTBC = 0;
    // Check and Set NSS value, it should be minimum of transmit and received antenna count
    phy->NSS = min((phy->nNTX < phy->nNRX ? phy->nNTX: phy->nNRX),nNSS_MAX);
    
    // Set NSTS value 
    phy->NSTS = min(phy->NSS  + phy->PHY_TYPE.ofdmPhy_11n.nSTBC,nNSTS_MAX);
 
    // Set  HT_DLTFs  Table 20-12—Number of HT-DLTFs required for data space-time streams
    phy->N_HT_DLTF = phy->NSTS;
    if(phy->NSTS == 3) 
        phy->N_HT_DLTF = 4;
 
    // Set NESS   NESS + NSTS <= 4
    phy->NESS =  nNSTS_MAX - phy->NSTS;
    
    // Set HT_ELTFs Table 20-13—Number of HT-ELTFs required for extension spatial streams
    phy->N_HT_ELTF = phy->NESS;
    if(phy->NESS == 3)
        phy->N_HT_ELTF = 4;
    
    // Set total HT_LTF = HT_DLTF + HT_ELTF
    phy->N_HT_LTF = phy->N_HT_DLTF + phy->N_HT_ELTF;
    if(phy->N_HT_LTF > 5) // Max is 5
        phy->N_HT_LTF = 5;
 
    phy->dControlFrameDataRate = fn_NetSim_IEEE802_11_HTPhy_getCtrlFrameDataRate(phy);
}
 
double get_11n_preamble_time(PIEEE802_11_PHY_VAR phy)
{
    double dTGF_HT_PREAMBLE;
    int nSignalExtension = 0;
 
    dTGF_HT_PREAMBLE = phy->PHY_TYPE.ofdmPhy_11n.nTHT_GF_STF \
        + phy->PHY_TYPE.ofdmPhy_11n.nTHT_LTF1 \
        + ((phy->N_HT_LTF - 1) * phy->PHY_TYPE.ofdmPhy_11n.nTHT_LTFs);
 
    return dTGF_HT_PREAMBLE + 
        phy->PHY_TYPE.ofdmPhy_11n.nTHT_SIG +
        nSignalExtension;
}